應用膀胱掃描儀評估攝護腺癌放射治療時的膀胱體積：更好的脹膀胱方法？

Abstract

研究目的：放射治療是對未轉移攝護腺癌的主要治療之一。然而，接受過攝護腺放射治療的男性約5%-10%會出現放射性膀胱炎，為避免上述副作用，可考慮喝水脹膀胱，以減少膀胱接受到的輻射劑量。膀胱掃描儀是超音波的設備，具有在放射治療攝護腺癌時評估膀胱大小的潛在用途。因此，進行了此單一機構的前瞻性先導研究。 方法：自2017年12月至2019年3月，收錄11位接受導航螺旋刀放射治療攝護腺癌之男性。為驗證膀胱掃描儀的準確度，將其測量值與重組的百萬伏特電腦斷層計算得到之膀胱體積做比對。我們假設膀胱掃描儀對病人脹膀胱有幫助，故採單組交叉研究設計，藉由不同的脹尿方式將放射治療而分為二階段，第一階段 (傳統方法)—患者需在排空膀胱後，喝定量的水並等待固定的時間；第二階段 (膀胱掃描儀回饋方法)—脹膀胱的步驟依據膀胱掃描的量測值。VBS是放射治療前經由膀胱掃描儀所測量之膀胱大小的三次平均讀值；VCT是由百萬伏特電腦斷層影像獲得的膀胱體積。 結果：研究發現VBS與VCT有高度的相關性，相關係數為0.87 (95%信賴區間：0.84-0.90)。線性混合模式發現：表示準確性的預測斜率係數為0.65 (95%信賴區間：0.60-0.69)、截距項為53毫升、需考量隨機效應。相較於傳統方法，膀胱掃描儀回饋方法可得到較大的膀胱體積，兩種方法所得到膀胱體積之平均差值為36.9毫升 (95%信賴區間：24.5-49.3毫升)。當定義脹尿失敗為VCT未達計畫體積的80%，使用膀胱掃描儀回饋方法可降低失敗率，其勝算比為0.44 (95%信賴區間： 0.19-0.72) 而絕對風險減少9.1% (95%信賴區間：0.2%-19.9%)。 結論：我們的研究結果支持膀胱掃描儀的準確度。膀胱掃描儀回饋方法可幫助病人適當地脹膀胱，達到較大的膀胱體積以及降低脹膀胱的失敗率。

Introduction: Radiotherapy is one of the definitive treatments for men with localized prostate cancer. However, approximately 5%-10% of men receiving prostate radiotherapy may suffer from radiation cystitis. A way of limiting radiation cystitis is bladder filling, which results in less radiation dose to the bladder. BladderScan, an ultrasound-based bladder volume scanner, has a potential for use in evaluating bladder volume during radiotherapy for prostate cancer. Thus, a prospective pilot study was initiated in a single institution. Methods: From December 2017 to March 2019, eleven men receiving TomoTherapy for localized prostate cancer were enrolled. We tested the validity of the BladderScan by comparing the measurements with the calculated volume reconstructed by megavoltage computed tomography (MVCT) scans. Then we hypothesized that the BladderScan feedback method would help patients fill the bladder adequately. For a single-arm crossover design, the radiotherapy was divided into two sequences by different methods of bladder filling. Sequence 1 (conventional method): the patient was asked to drink water after voiding urine. The amount of water and the length of waiting time should be the same as the setting of the CT simulation. Sequence 2 (BladderScan feedback method): the bladder filling procedure depended on the BladderScan measurements. VBS was the mean volume of three measurements by BladderScan. VCT is the bladder volume derived from the MVCT. Results: A highly correlated result between the VBS and VCT with the correlation coefficient of 0.87 (95% CI: 0.84-0.90) was noted. The linear mixed model showed the estimated slope parameter, represents the accuracy of BladderScan was 0.65 (95 % CI: 0.60-0.69), while the intercept was 53 ml with a random effect. The BladderScan feedback method resulted in a larger bladder volume than did the conventional method, with a mean difference of 36.9 ml (95% CI: 24.5-49.3 ml). When the failure was defined as the VCT less than 80% of planned volume, the BladderScan feedback method brought about a relative reduction in failure rate with the odds ratio as 0.44 (95% CI: 0.19-0.72) and an absolute reduction by 9.1% (95% CI: 0.2%-19.9%). Conclusion: The validity of the BladderScan was supported from the results of our study. The BladderScan feedback method would help patients fill the bladder adequately, with a larger bladder volume and a lower failure rate of bladder filling.